1. Field of the Invention
The present invention relates generally to window coverings and more particularly to fabric-type window coverings provided with adjustable vanes for controlling the amount of light passing therethrough.
2. Description of the Prior Art
Fabric window coverings are often preferred by consumers for a number of their features. The features most often considered desirable are the softer appearance relative to traditional venetian blinds, the uniform appearance which they provide a window, and insulating properties associated with cellular fabric shades.
Cellular fabric shades offering these features are known in the art. For example, U.S. Pat. No. 4,450,027 to Colson discloses cellular window coverings which may be made of fabric or film materials. In the process disclosed in the Colson patent, a flexible strip of material is folded into a continuous longitudinal tube and the longitudinal folds thus created are permanently set by passing the tubing material around a heat setting wheel. Adhesive is applied along one side of the flattened tubular material which is subsequently stacked by winding onto a rack having flat surfaces. The winding in this manner presses the adhesive to the next layer wound onto the rack to form a bonded unitary stack of closed tubular cells. When the ends are cut from the rack, the stack may be expanded and the permanently set creases provide a neat and uniform outward appearance.
U.S. Pat. No. 4,732,630 to Schnebly discloses a modification to the Colson process described above. In the Schnebly patent, a hot melted adhesive is applied to one side of the tubular material. After the flat tubular strips have been stacked and cut, they are placed in an oven under pressure and the hot melted adhesive is activated to bond the layers together.
Both of the above patents disclose window coverings which exhibit the desirable features discussed to this point. However, window coverings of that type lack one feature which is often desired by consumers. That feature is the ability to control the amount of light admitted through the window covering, similar to a traditional venetian blind. There have been some attempts to provide a fabric window covering with the ability to control the amount of light entering the room. However, these attempts have lacked one or more of the features discussed above and have been less than successful.
U.S. Pat. No. 3,384,519 to Froget discloses one such attempt. The window covering disclosed therein consists of two cloth layers spaced apart by moveable parallel and flexible fabric blades having each of their marginal edges heat welded to one of the moveable cloth layers. With this window covering, relative movement of the two cloth layers in a direction perpendicular to the blades changes the angle of the blades and thus controls the amount of light admitted through the article. A number of undesirable features of the Froget window covering derive from the fact that it is constructed utilizing a heat welding process. First, this limits the fabrics which may be utilized to thermoplastic materials. Also, heat welding necessarily requires a melting of at least some of the fibers of the materials bonded, thus providing an uneven outer appearance along the heat welds and producing unwanted crimps or creases in the materials which can result in failure of the fabric fibers. Further, heat welding is a relatively slow process which may require six or more seconds to create a bond over an extended length. This is too slow for application in high volume commercial production processes. Other draw backs of the Froget window covering are that heat welds are limited in strength and it is difficult to achieve uniformly straight heat-welded joints over an extended length.
U.S. Pat. No. 2,865,446 to Cole discloses a window covering in which a long rectangular piece of fabric is doubled back upon itself and a plurality of pleated elements are placed between the folded-over sheets. The pleated elements are an accordion-pleated fabric which extends when the two sides of the folded over fabric are moved relative to one another in a direction perpendicular to the accordion pleats. Such a window covering does not provide a uniform appearance because the accordion-pleated fabric located close to the top of the window covering does not expand to the same extent as the fabric closer to the bottom of the window covering. Also, it is very difficult to insure that such accordion-pleated fabric returns to its desired position after each expansion.
The construction of Cole inherently creates an undesirable feature if a woven-type sheer fabric is used for the folded over, long rectangular piece of fabric. That undesirable feature is a moire effect or interference pattern which would result when light is viewed through the folded over fabric. The Froget window covering would also appear to have this drawback because the embodiment shown in FIG. 8 of that patent appears to show front and back fabrics of the same material.
French Patent No. 1,309,194 discloses a curtain with variable opacity. In this curtain, screen or mesh parallel sides are provided with tiltable braids therebetween. The braids are said to be attached at their edges to the sides. However, no means for attachment is specified. The drawings appear to indicate a hinged-type attachment and the specification ends by stating that the difficulties of construction are substantial.
U.S. Pat. No. 3,851,699 issued to Shapiro discloses a vertical louver-type window drape wherein a continuous sheet of fabric material is interwoven with a plurality of relatively rigid vanes such that the vanes which are light impeding alternate with light transmitting sections of the fabric. One obvious drawback with a system of this type is that the vanes overlap the fabric requiring excessive fabric in order to fabricate the entire window covering. Further, the vanes or louvers are only attached to the fabric material along a top and bottom edge thereof, thereby inhibiting the control over the fabric material during operation of the window covering.
Another window covering showing the combination of relatively rigid vanes with a sheet of fabric is disclosed in U.S. Pat. No. 3,844,330 issued to Hyman. In the Hyman patent, vertically extending louvers have drape material hung thereover in a way such that a normal drape-like affect is obtained regardless of the angular orientation of the louvers. As with the system employed in the Shapiro patent, the sheet of fabric material in one arrangement is interwoven with the louvers thereby requiring excessive fabric, whereas in another embodiment the fabric is merely attached to a side edge of the louver to create a different visual affect. While the patent acknowledges that the fabric material may be attached to the louvers along the full length of the louvers, it is expressed that a desirable arrangement is to merely attach the fabric to the louvers along an upper edge to provide a full drapery-like affect.
It is to improve upon the shortcomings in the prior art fabric window coverings that the present invention has been made.